The invention relates to a device for clamping mouldings prior to stapling, in a frame assembling machine.
The frames designed to surround pictures are known to be manufactured from framing strips, beads or mouldings by cutting the latter to a mitre shape for subsequent assembly. To assemble these mouldings, use is advantageously made of a staple formed of a metallic strip bent in two in the vicinity of its median part, one of the horizontal edges of which has a bevelled part formed from the internal face of the staple and the vertical edges of which are bent back outwardly in the direction of the bending axis.
For stapling properly speaking, there is known a machine comprising a table with a 90° notch on its forward face, and means for applying the mitre faces of the framing strips against one another under pressure.
More precisely, these means are constituted by a mobile plate, the front part of which forms a 90° angle so that its faces move parallel to those of the notch, as well as two claws borne by said plate the role of which is, when the plate is moved forward, to exert a pressure against the mouldings and to clamp them in this way against one another and against stops, prior to stapling properly speaking. One of the claws is slideable on the mobile plate, and return biased by a pressure spring. The other claw, which is also return biased by a spring, is pivotable on the plate and its pivoting movement is produced in the direction of clamping of a moulding, when the plate itself moves forward, thanks to a projection serving as a stop.
It is thus the movement of the mobile plate in the direction of the table bearing the mouldings that causes the action of the claws by translation or rotation. The return springs of the claws therefore have to be calibrated correctly so that the pressure that they exert on the mouldings is sufficient but not excessive, and these calibration operations prove to be quite a delicate matter. The Applicant has also noted that the pressure that the pivoting claw could exert can vary according to the dimension of the mouldings and the distance that can be given to the mobile plate in relation to the fixed table, since the clamping of this pivoting claw is linked to the advance of said plate.